The apical brush border membranes of normal mucosal cells lining the small and large intestine express a specific receptor, guanylyl cyclase C (gcC, hereinafter “ST receptor”). ST receptors are unique in that they are localized in the apical brush border membranes of normal cells lining the intestinal tract. Indeed, they are not found in any other normal cell type in placental mammals. It has been shown that normal gastric and esophageal cells do not express the ST receptor. The discovery has been made that primary and metastatic gastric and esophageal cancer cells express the ST receptor. In addition, ST receptor transcription products, such as mRNAs for the ST receptor protein and the ST receptor mRNA splice variant CRCA-1 are markers for gastric and esophageal cancer cells.
The ST receptors located in the lining of the small and large intestine are almost exclusively localized to the apical membranes, with little being found in the basolateral membranes on the sides of intestinal cells. Of significance is the fact that mucosal cells lining the intestine are joined together by tight junctions which form a barrier against the passage of intestinal contents into the blood stream and components of the blood stream into the intestinal lumen. Therefore, the apical location of ST receptors isolates these receptors from the circulatory system so that they may be considered to exist “outside the body” and the rest of the body is considered “outside the intestinal tract.” Compositions administered “outside the intestinal tract” are maintained apart and segregated from the only cells which normally express ST receptors.
E. coli produce a small heat-stable toxin (ST) that is responsible for endemic diarrhea in developing countries and travelers diarrhea. This toxin induces intestinal secretion by binding to ST receptor in the apical brush border membranes of the mucosal cells lining the small and large intestine. Binding of toxin to these receptors triggers a cascade of biochemical reactions in the apical membrane of these cells resulting in the production of a signal which induces intestinal cells to secrete fluids and electrolytes, resulting in diarrhea. Two homologous peptides to ST are guanylin and uroguanylin, both of which are produced locally in the intestine.
The discovery that a large proportion of metastasized colorectal cells, and primary and metastatic gastric and esophageal cancer cells, including those found in liver, lung, bone, brain, nodes and peritoneum tissues, express ST receptors on their cell surfaces, even at highly undifferentiated stages gave rise to several inventions. Given that ST receptor expression is generally tissue-specific to normal cells lining the inside of the colon, the discovery of expression of ST receptors on the surfaces of metastatic colorectal tumor cells, as well as primary and metastatic gastric and esophageal cancer cells, provides a target for delivering imaging and therapeutic agents to these cells and provides a means for detecting and identifying cells of colorectal, gastric and esophageal origin in samples.
U.S. Pat. Nos. 5,518,888, 5,879,656, 6,060,037, and 6,268,159, which are each incorporated herein by reference, describe technologies which target metastasized colorectal tumor cells using compounds that specifically bind to ST receptors. Compounds which bind to ST receptors and which are either detectable or therapeutically active are administered to an individual parenterally. The compounds localize to the metastasized colorectal tumor cells through their affinity to ST receptors expressed by the cells.
U.S. Pat. Nos. 5,601,990, 5,731,159, 5,928,873, and 6,060,037, which are each incorporated herein by reference, describe technologies which detect ST receptor expression in extraintestinal samples as a means of detecting the presence of metastatic colorectal tumor cells. ST receptors and transcription products encoding ST receptors serve as molecular markers whose presence in extraintestinal samples indicates metastasized colorectal tumor cells and tumors of colorectal origin. ST receptor protein and nucleic acid molecules encoding ST receptor protein are detected in various ways such as, for example, immunoassays and PCR assays.
In addition to its use for targeting in in vivo therapeutics and diagnostic/imaging protocols as well as its use for targeting in in vitro diagnostic protocols, the tissue specific expression of ST receptor in cells of colorectal origin has also been exploited in methods and compositions for drug delivery, for example gene therapy. Cells that express ST receptor, i.e. cells of colorectal origin, including normal as well as cancer cells or primary and metastatic gastric and esophageal cells, can be specifically targeted. U.S. Pat. No. 5,962,220 and U.S. Pat. No. 6,087,109, which is incorporated herein by reference, describes the use of compounds which bind to ST receptors such as native ST or other ST receptor binding ligands, as ST receptor binding moieties used to deliver nucleic acid molecules such as antisense agents to colorectal cells by targeting ST receptors which are expressed by such cells.
Moreover, vaccines have been designed which induce an immune response against ST receptors and thus can be used to prophylactically and/or therapeutically immunize an individual against metastasized colorectal cancer. PCT application PCT/US97/07565, which is incorporated herein by reference, describes such vaccines and the uses therefor.
U.S. application Ser. No. 819,249 filed Mar. 27, 2000 and published Oct. 11, 2001 as U.S. Application Publication Number 20010029019, which is incorporated herein by reference, describes using ST receptor (GCC) as a marker for detection of Gastric and Esophageal Cancer and as a target for delivery of imaging and therapeutic agents against Gastric and Esophageal Cancer cells.
Moreover, vaccines have been designed which induce an immune response against ST receptors and thus can be used to prophylactically and/or therapeutically immunize an individual against metastasized colorectal cancer. PCT application PCT/US97/07565, which is incorporated herein by reference, describes such vaccines and the uses therefor.
There remains a need for improved methods of inhibiting the proliferation of colorectal, gastric and esophageal cancer cells. There remains a need for improved methods of inhibiting primary colorectal, gastric and esophageal cancer cells from metastasizing and metastasized colorectal, gastric and esophageal cancer cells from further metastasizing. There remains a need for improved methods of treating primary and metastasized colorectal, gastric and esophageal cancer in vivo. There remains a need for methods of inhibiting the development of colorectal, gastric and esophageal cancer from polyps and precacerous lesions in vivo. There remains a need for improved in vitro methods of and reagents and kits for treating metastasized colorectal and primary and metastatic gastric and esophageal cancer. There remains an need for improved methods of and compositions for treating, imaging and detecting metastasized colorectal cancer in vivo. There remains an need for improved in vitro methods of and reagents and kits for diagnosing metastasized colorectal cancer and of identifying cancer as being of colorectal origin. There remains an need for improved methods of delivering compounds to colorectal cells. There remains a need for improved vaccines for preventing and treating metastasized colorectal cancer.